Polypivalolactone fibers and a method for their manufacture

ABSTRACT

A DRAWN, TENACIOUS POLYPIVALOLACTONE FIBER HAVING A DENSITY OF 1.17 AT THE MOST AND A SUFFICIENT HEAT-SETTING ABILITY WHICH COMPRISES A POLYMER CONSISTING ESSENTIALLY OF POLYPIVALOLACTONE WHICH CAN BE OBTAINED BY UNIFORMLY INCORPORATING A POLYMER CONSISTING ESSENTIALLY OF POLYPIVALOLACTONE WITH A SMALL AMOUNT OF A LEAST ONE ORGANIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE, PARTIALLY OXIDIZED POLYETHYLENE, COPOLYMERS OF ETHYLENE AND A,B-ETHYLENIC UNSATURATED CARBOXYLIC ACID, POLYETHYLENE OXIDE, PARAFFINIC HYDROCARBONS, ESTERS OF PHOSPHORIC ACID AND ESTERS OF PHOSPHOROUS ACID, EXTRUDING THE MIXTURE THROUGH AN ORIFICE OF A SPINNERET, APPLYING HIGH DRAFT TO THE EXTRUDED MIXTURE WHILE IT IS STILL IN A MOLTEN OR PLASTICIZED STATE TO THEREBY FORM UNDRAWN FIBERS, AND THEREAFTER, DRAWING SAID UNDRAWN FIBER. SAID UNIFORM ADMIXTURE OF SAID COMPOUND LEADS TO BROADENED RANGES OF THE CONDITIONS SUITABLE FOR SPINNING, IMPROVED FEASIBILITY OF OPERATION, RETARDATION OF CRYSTALLIZING VELOCITY OF THE POLYMER AFTER BEING SPUN AND SOLIDIFIED, AND MARKEDLY IMPROVED ORIENTATION.

United States Patent Ofice Patented Apr. 20, 1971 US. Cl. 260-28 8 Claims ABSTRACT OF THE DISCLOSURE A drawn, tenacious polypivalolactone fiber having a density of 1.17 at the most and a sufilcient heat-setting ability which comprises a polymer consisting essentially of polypivalolactone which can be obtained by uniformly incorporating a polymer consisting essentially of polypivalolactone with a small amount of at least one organic compound selected from the group consisting of polyethylene, partially oxidized polyethylene, copolymers of ethylene and ufi-ethylenic unsaturated carboxylic acid, polyethylene oxide, paraffinic hydrocarbons, esters of phosphoric acid and esters of phosphorous acid, extruding the mixture through an orifice of a spinneret, applying high draft to the extruded mixture while it is still in a molten or plasticized state to thereby form undrawn fibers, and thereafter, drawing said undrawn fiber. Said uniform admixture of said compound leads to broadened ranges of the conditions suitable for spinning, improved feasibility of operation, retardation of crystallizing velocity of the polymer after being spun and solidified, and markedly improved orientation.

BACKGROUND OF THE INVENTION (a) Field of the invention The present invention relates to a method for manufacturing highly oriented and tenacious fibers which comprise a polymer consisting essentially of polypivalolactone (which will hereinafter be referred to merely as polypivalolactone fibers) by melt spinning highly crystalline polypivalolactone and subsequently drawing the spun undrawn fibers.

The preferred utility of the polypivalolactone fibers manufactured, according to the method of the present invention, as filaments or staple rfibers covers a wide range from garments to industrial purposes, such as woven fabrics, knitted goods, carpets, nonwoven cloths, felt, web cloth material for synthetic leathers, paddings, papers, filtering cloths and tire cords.

(b) Description of the prior art In order to make a useful fiber by melt spinning a fiberforming thermoplastic organic synthetic linear polymer, such as a polyamide and a polyester, it has been generally accepted as being necessary to include a step of drawing the fiber after the latter is spun. Specifically, it is known that the so-called undrawn fibers after being spun have an extremely low degree of orientation of the molecular chains in the polymer. Especially those undrawn fibers consisting of a polymer, such as a polyester, also have an extremely low degree of crystallinity and are poor in mechanical strength required of such fibers. Their orientation and crystallinity can be improved by subjecting them to drawing and it is only after the undrawn fibers are drawn that the fibers can acquire the mechanical strength desired of such fibers. It is also known that in order to facilitate the orientation by drawing of fibers consisting of a highly crystalline polymer in the stage after the meltspinning step, it has been the practice to lead the fibers into a quenching liquid medium immediately after they are spun and before drawing, while the fibers are still in a molten or plasticized state, to rapidly cool and solidify the polymer by such quenching and to thereby minimize their degree of crystallinity and also to produce an amorphous molecular arrangement.

In view of the characteristics of polypivalolactone polymer, that it crystallizes rapidly and easily to a very high degree, it is impossible to expect sufficient orientation of the molecules in the polypivalolactone rfibers nor is it possible to expect to obtain fibers having a superior physical property, from the application of the aforesaid melt-spinning or drawing conditions of the prior art. This is endorsed by the statement made in the specification of the French Pat. No. 1,231,163 and the paper of R. Thiebaut et a1. (Industrie des Plastiques Modernes, Mar. 13, 1962), both of which point out that there is a tremendous difficulty in manufacturing fibers from polypivalolactone on an industrial basis because of the inconveniences that, owing to the unusually high crystallinity of polypivalolactone, the amorphous molecular arrangement cannot be acquired from the mere quenching of this polymer at the time of the formation of a film. This polymer attains a maximum degree of crystallinity during a very short period of time, resulting in an opaque film. Also, during the step of producing a fiber, this polymer crystallizes rapidly immediately after the melt-spinning, making the orientation by subsequent drawing extremely difficult so that the resulting fibers are brittle and lack desirable mechanical properties. Because of the fact that the production of fibers from polypivalolactone is accompanied by these great difliculties, there have been made very few studies on the techniques of manufacturing fibers from this polymer, except for the statements dealing with a few manufacturing conditions which are made in the specifications of US. Pat. No. 2,658,055, British Pat. No. 766,347 and Japanese Pat. Publication No. 9810/ 1966. Specifically, US. Pat. No. 2,658,055 contains a statement reading to the effect that polypivalolactone develops an orientability when it has a molecular weight corresponding to an intrinsic viscosity (n) of 0.5 or more, and polypivalolactone having such a molecular weight can be subjected to melt spinning. In Example 4 of the specification of said US. patent, it is described that by extruding polypivalolactone at a temperature just below the melting point, namely, in the range of from 230 degrees centigrade to 235 degrees centigrade and under a high pressure of 4,000 pounds per square inch and by thereafter manually drawing the extruded fiber to a length four times the original length, a drawn fiber showing an X-ray orientation angle of 17 degrees was obtained. In Example 5 thereof, there is described the acquisition of a [fiber having a high degree of crystallinity, such as a density of 1.20 (24.5 degrees centigrade), by a method similar to the above from polypivalolactone having an intrinsic viscosity (n) of 0.90.

British Pat. No. 766,347 discloses in Example 7 the fact that, by melt spinning polypivalolactone at a temperature above its melting point, namely, at 285 degrees centigrade, and by drawing the fiber to a length four times the original length at degrees centigrade, a fiber having such properties as are represented by a tensile strength of 1.9 gr./d. and an elongation of 19.9 percent was obtained.

However, the method of said US. patent requires an extremely high pressure at the time of spinning and, therefore, it is ditficult to apply this method industrially since there are involved various problems with respect to the feasibility of the operation, the property of the produced fiber and the designing of the manufacturing apparatus, and also from the viewpoint of the maintenance of the apparatus. Especially, the high density (1.20) of the fiber obtained according to this prior method means that the degree of crystallinity of the polymer constituting the fiber is close to the maximum value which this polymer can attain, and that the heat-setting ability of the fiber is already lost. Accordingly, this shows, for example, the fact that it is impossible to manufacture a crimped fiber of an excellent quality.

Also, with the property of the fiber obtained from the application of the method of said British patent, one could not expect a superior position of this fiber in industry over other fibers. Furthermore, the Japanese Patent Publication No. 9810/1966 carries a mere general statement that such fibers are given the necessary orientation by the application of a large draft effect during melt spinning and then the degree of orientation of such fibers may be augmented by conducting drawing immediately after the fibers are melt spun. However, this publication lacks a clear cognizance of the optimum spinning conditions.

SUMMARY OF THE INVENTION After an extensive and detailed research on the physical property and the fine structure of polypivalolactone, the inventors have discovered that while this polymer belongs to the family of polyesters, as will be seen from its chemical structure, it is an extremely unique polymer which is completely different, in both its physical character and fine structure, from other fiber-forming polyesters which are represented by, for example, polyethylene terephthalate and similar polyesters. After further detailed and systematic study on the spinnability of polypivalolactone, it has been found that the spinning method and the spinning condition for ordinary polyester fibers can never be applied to polypivalolactone. Rather, the same requires new, specific spinning conditions and that by the application of a spinning method incorporating the new, specific spinning conditions, it becomes possible to manufacture a highly oriented, tenacious, transparent fiber having a suflicient heat-setting ability and a desirable elastic recovering ability which can never be obtained by the prior spinning methods, and, based on such knowledge, the inventors have discovered an improved method.

As a result of the subsequent continuous detailed research on the relationship between the rheological property and the spinnability of polypivalolactone at the time of melting, the inventors have found that, while the rheological property of the melted polypivalolactone depends a great deal on the temperature and the pressure employed at the time of melting as compared with other polymers used in ordinary melt spinning, this high degree of dependency of the rheological property of polypivalolactone on the temperature and the pressure can be substantially minimized and stabilized by incorporating, with polypivalolactone, at least one organic compound selected from the group consisting of polyethylene, partially oxidized polyethylene, copolymers of ethylene and a,B-ethylenic unsaturated carboxylic acids, polyethylene oxides, paraffinic hydrocarbons, esters of phosphoric acid and esters of phosphorous acid. Also, this minimized and stabilized dependency of the rheological property of polypivalolactone on the temperature and the pressure at the time of melting is extremely effective in broadening the range of the appropriate Spinning conditions as well as for improving the efficiency of the operation, the spinnability of the molten polymer at the time of spinning, and improving its detachability from the nozzle, and also in retarding the rapid crystallization of the polymer after the spun fiber is solidified, and further for the improvement of the orientation effected at the time of spinning under draft and during the subsequent drawing step.

It is, therefore, an object of the present invention to provide a polypivalolactone fiber which is highly oriented and which has sufiicient heat-setting ability and which 4 is tenacious, transparent, uniform in quality and greatly useful.

Another important object of the present invention is to provide an improved industrial method for quite easily manufacturing such a useful fiber by spinning and drawing a polypivalolactone fiber without the need for any special mechanical equipment.

Still another object of the present invention is to provide an industrial manufacturing method in which desirable manufacturing conditions for obtaining such fiber are specified.

Yet another object of the present invention is to provide a crimped fiber consisting essentially of polypivalolactone and having a markedly superior extension percentage of crimp and recovery percentage of crimp.

Other objects of the present invention will become apparent by reading the following description.

While the present invention concerns the techniques of melt spinning and drawing a polymer consisting essentially of polypivalolactone, it is to be understood that said polymer is such that it is incorporated uniformly, prior to being subjected to melt extrusion, with a small amount of an additive which consists of at least one organic compound selected from the group consisting of polyethylene, partially oxidized polyethylene, copolymers of ethylene and o fl-ethylenic unsaturated carboxylic acids, polyethylene oxides, parafiinic hydrocarbons, esters of phosphoric acid and esters of phosphorous acid.

The term polymer consisting essentially of polypivalolactone used in the present invention means polypivalolactone or a copolymer or blend polymer of polypivalolactone as the principal component with other polymer or polymers.

The term polypivalolactone which is used in the I present invention means a linear condensation polymer consisting essentially of recurring ester structural units expressed by the formula:

This polymer is readily manufactured by the method of polymerization of hydroxypivalic acid or its ester as is described in US. Pat. No. 2,658,055 or by the employment of the method of polymerizing pivalolactone as is described in the specification of British Patent No. 766,347. The term a copolymer of polypivalolactone means a copolymer which is prepared by copolymerizing the aforesaid polypivalolactone with up to 25 mol. percent of other lactones, such as fi-propiolactone, mot-Cliethylpropiolactone. A blend polymer of polypivalolactone as the principal component and of other polymer or polymers is a composition consisting of polypivalolactone or a copolymer of polypivalolactone as the principal component which is blended with other polymer or polymers in an amount essentially not affecting the property of said principal component. It is needless to say that polypivalolactone containing ordinary additives, such as a dye, a pigment and a stabilizer, is also usable.

It is necessary that the polypivalolactone which is applicable to the present invention have an intrinsic viscosity (17) ranging between 0.7 and 5.5, and preferably in the range between 0.8 and 4.0. Polypivalolactone having (1 less than 0.7 is markedly low in fiber-forming ability, and unless it is given an extremely high spinning draft at the time of spinning, the fiber cannot be endowed with utility, nor can it exhibit such excellent properties as are obtained by the present invention. A very high value of intrinsic viscosity, on the other hand, will result in a restriction of the fiber manufacturing conditions. Specifically, in case (n) has a value exceeding 5.5, there will occur an extreme lowering of the fluidity of the polymer in its molten state and this will give rise to a difiiculty in the spinning operation. In general, however, there is an advantage that the degree of orientation of an undrawn spun fiber can be increased by the application of a smaller amount of spinning draft as (1 increases in value, provided that the efficiency of the spinning operation is not taken into account, and as a result, it becomes easy to produce a tough fiber.

The intrinsic viscosity (1;) is determined by the use of a mixed solvent consisting of six parts of phenol and four parts of orthochloro-phenol and by the employment of a temperature of 30 degrees centigrade and it is calculated from the following equation:

wherein: 0 represents the concentration expressed in grams of polypivalolactone contained in 100 ml. of solution formed by dissolving polypivalolactone in the aforesaid solvent;

1 is defined by (1717O/17, in which n represents the viscosity of the aforesaid solution, and n repreents the viscosity of said solvent.

The paraffinic hydrocarbons used in the present invention are alkanes by the general formula C H and having a straight chain structure in which 21514, and include, for example, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, dotriacontane, pentatriacontane, tetracontaine, pentacontane, hexacontane, dohexacontane, tetrahexacontane and heptacontane. Furthermore, the paraffins consisting chiefly of normal parafiins, namely, those commercial parafiins which contain a small amount of such substances as isoparafiin and cycloparaflin besides these normal paraffins, are also usable.

Normal parafiins having less than 14 carbon atoms invariably have relatively low boiling points. Accordingly, they volatilize at a high temperature, for instance, when they are in the melt-spinning process, and they do not bring forth the desired effect. Therefore, such normal parafiins are not suitable for being used in the method of the present invention. Normal paraffins include those occurring in nature, for example, those contained in petroleum oil and also those obtained by synthesis. However, naturally occurring normal paraffins and refined natural normal parafiins are more advantageous from the viewpoint of the price. As for the naturally occurring normal parafiins, those up to heptacontane, which have 70 carbon atoms are well known. Those having molecular weights up to this order can be used in the method of the present invention. In other words, any paraffiuic hydrocarbons having 14 or more carbon atoms can be used. However, those having lesser molecular weights display a greater effect, and accordingly, the amount of those to be added can be reduced. Polyethylenes can also be used effectively in the present invention. Polyethylenes having a low mean molecular weight can be regarded in substantially the same light, from the viewpoint of chemical structure, as paraffinic hydrocarbons having high molecular weight. Polyethylenes which are used in the present invention include those which are manufactured according to the so-called high pressure process, medium pressure process and low pressure process. Especially, polyethylenes having a melt index of 20 or more, and preferably 30 or more, are effective for the attainment of the objects of the present invention. Those polyethylenes having a melt index smaller than the above-mentioned lower limit, namely, those of a higher molecular weight, are poor in the ability of improving the rheological property of poly ivalolactone and are not suited for use in the present invention.

Partially oxidized polyethylenes which are used in the present invention are such that their methyl radicals located in the end group and side chains have been partly oxidized and converted to carboxylic radicals. Copolymers of ethylene and at least one (LfiCthYlCHiC unsaturated 6 carboxylic acid can also be effectively used in the present invention. Such carboxylic acids include, for example, acrylic acids, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, citraconic acid and mesaconic acid. These copolymers possess chemical structures which are similar to those of the partially oxidized polyethylene. Such ethylene copolymers can be obtained by copolymerizing ethylene and one or more of said u,n-ethylenic monomers. Various methods for use in the synthesis of such olefin copolymers are known from a number of literature disclosures. One example of the preferred methods comprises introducing a mixture of two monomers, such as those mentioned above, together with a free radical polymerization initiating agent, such as a peroxide, into a polymerizing zone held under a high pressure between 10 and 3,000 atmospheres and at a high temperature between degrees centigrade and 300 degrees centigrade. Polymerization may be carried out by the use of a solvent, such as water or benzene, which is inactive toward the reaction system, or it may be performed essentially as bulk polymerization. Polyethylene oxide, which is a completely different form of partially oxidized polyethylene, can also be satisfactorily used as an additive in the present invention. Polyethylene oxide can be readily obtained by subjecting an ethylene oxide to ring opening polymerization by the use of a Friedel-Crafts type catalyst or an alkaline or acidic catalyst. Among the polyethylene oxides, those having a molecular weight of about 600 or more are particularly suitable for the purposes of the present invention. Furthermore, esters of phosphoric acid and phosphorous acid can also be used effectively as an additive in the present invention. They include, for example, tricresyl phosphate, trixylenyl phosphate, trinonyl phosphite and trioctadecyl phosphite. These additives can be used either independently or in the form of a miXture of two or more of them.

The suitable range of the amount of the foregoing additives to be used is between 0.1 and 10.0 percent by weight, and preferably, between 1.0 and 6.0 percent by weight of the total weight of the composition comprising a polymer consisting essentially of polypivalolactone and the additives. Those additives having a low molecular weight display a sufiicient effect by being used in a small amount. In the event that the amount added is less than 0.1 percent by weight, however, it does not bring about a substantial effect on the improvement in the drawability of the spun fiber in the steps subsequent to the first step, as compared with the instance where no additive is used. In the event that the amount is in excess of 10.0 percent by weight, on the other hand, the result will be a reduced spinnability which will be accompanied by a reduction in the uniformity of the size of the final fiber.

The aforesaid additives are incorporated, either independently or as a mixture of two or more of them, with polypivalolactone after the completion of the polymerization of polypivalolactone and are mixed thoroughly therewith while being stirred so that the additive may be dispersed uniformly. Polypivalolactone containing such additive in the state of a uniform dispersion is transferred to the first step, namely, the melt-spinning step either directly or after 'being shaped into granules or chips. Satisfactory results can be obtained also by transferring granules or chips of polypivalolactone not containing the aforesaid additive uniformly dispersed therein but having such an additive adhering thereto or mixed therewith to the first step. In case the additive consists of a paraffinic hydrocarbon, it is possible to introduce a solution in which the paraffinic hydrocarbon is completely dissolved in a solvent which is capable of dissolving the hydrocarbon, into polypivalolactone to be absorbed thereby, and thereafter to transfer the resulting polypivalolactone, which has been stripped of said solvent by evaporation, to the spinning step. When required, such polypivalolactone may be melted to effect a thorough mingling of the additive in the polypivalolactone and then made into chips before being transferred to the spinning step. In any case, it is important that the aforesaid additive which has been incorporated 'with polypivalolactone be present therein in such a state that the additive is uniformly dispersed or mingled in the polypivalolactone by a mechanical opera tion, such as mixing by stirring, 'while in the melted state. This mixing by stirirng may be carried out by means of a screw housed in an apparatus such as a melt extruder or by means of a pump or like means.

The aforesaid additive, which is thus added and dis persed in polypivalolactone, retains its state of being molten, mingled and dispersed in the molten polypivalolactone for an extended period of time. The additive contained in the aforesaid form in polypivalolactone displays the following named various excellent effects in association with the subsequent steps, without separating from the mixed state under normal melt-spinning conditions and without affecting in any way the desirable chemi cal as well as physical properties of polypivalolactone:

(a) It minimizes as well as stabilizes the great dependency of the melting and rheological property of polypivalolactone on the temperature and pressure employed;

(b) It contributes to the attainment of the broadening of the range of the intrinsic viscosity of polymers suitable for spinning and also to the enhancement of the feasibility of operation;

(c) It improves the spinnability of the molten polymer and detachability of the molten polymer from the nozzle;

((1) It retards the rapid crystallization of the polymer in the stage after the spun fiber is solidified;

(e) It extremely improves the orientation in the steps of spinning and drawing.

As has been described above, the polypivalolactone which has been mixed uniformly with an additive can be spun and drawn easily by the use of a known melt-spinning and take-up apparatus and drawing apparatus, without requiring any special mechanical equipment.

The description will hereafter be directed to the manufacturing method of the present invention, which will be made in the order of the series of steps.

In the first step, polypivalolactone which has been melted in a known melt-spinning apparatus is extruded in fiber form through an orifice of a spinneret. The temperature employed in this melt-spinning step is in the range between 240 degrees Centigrade and 310 degrees centigrade. In general, the fluidity of a polymer increases with the elevation of the temperature, resulting in an improved spinnability. When the temperature of the polypivalolactone exceeds 280 degrees Centigrade, however, it tends to become difiicult to control the melt viscosity at the time of spinning and also the spinning conditions due to various reasons, including thermal decomposition of the polymer. In such case, however, the use, either independently or in combination, of a known heat stabilizer such as 4,4 thio-bis (6-tert-butyl-m-cresol), 4,4-butylidene-bis ('6 tert-butyl-m-cresol) and di-lauryl-thio-dipropionate which are usually applied to poly-a-olefin or rubbers, will make it possible to perform the spinning smoothly at a temperature up to 310 degrees centigrade without essentially being accompanied by hazards, such as thermal decomposition. Also, at a temperature of lower than 240 degrees centigrade, which is the melting point of the polymer, it is practically difficult to perform satisfactory spinning unless an extremely high pressure is applied. Such a low temperature also gives rise to various problems relating to: the efficiency of the operation, the property of the final yarn, the uniformity of the fiber as well as the apparatus and equipment to be used, and therefore, such low temperature is not suited for the purposes of the present invention. As for the melt-spinning apparatus, any known apparatus, such as a grid melter and a screw extruder-type apparatus, may be employed as desired. In case it is desired to perform melt spinning at a relatively low melt-spinning temperature,

a screw extruder is advantageously used. With respect to the diameter of the orifice of the spinneret, there is no particular restriction thereon. However, it is necessary to select the size of the orifice so as to comply with the size of the desired drawn fiber by taking the spinning deformation ratio, which is to be given in the second step, into account. The term spinning deformation ratio herein referred to means the ratio of the cross-sectional area of the polymer at the moment of extrusion through the orifice of the spinneret to the cross-sectional area of the undrawn fiber after being quenched and solidified, and it has a close relationship with the degree of orientation of the undrawn fiber. While the rheological property of molten polypivalolactone depends greatly on the temperature and the pressure employed, as compared with other polymers for use in melt spinning, such great dependency can be minimized and stabilized when the polypivalolactone is admixed with an additive. Thus, the use of an additive contributes to a marked improvement in the spinnability of the molten polymer and the detachability of the molten polymer from the nozzle and, accordingly, the workability in the spinning process is extremely improved. While polypivalolactone polymers have the shortcoming that those with a greater molecular weight have a higher melt viscosity and accordingly result in a reduced efficiency of operation, it is to be noted that, because the spinnability is markedly improved by the admixture of an additive, a polypivalolactone polymer having a markedly high molecular weight can be easily spun.

The polypivalolactone which is melt extruded from the orifices of the spinneret in the first step is immediately given the required amount of high draft in the second step. In doing so, it is important to carefully take into consideration the characteristics of the polymer, namely, that it is of a high degree of crystallinity and that its crystal is fairly rigid. The crystal of polypivalolactone being considerably rigid, the degree of its crystallinity is not at all reduced even when the temperature is elevated to the vicinity of its melting point (240 degrees Centigrade), and thus, polypivalolactone has a very narrow softening range. It is important that the polymer extruded from the orifice of a spinneret have a stress imparted thereto while it is still in the molten or plasticized state, or in other words, while it is at a temperature higher than 10 degrees centigrade below the melting point and more particularly while it is in the temperature range between 310 degrees Centigrade and 230 degrees centigrade, and that the polymer be thus transferred to such a drawable condition as is accompanied by the orientation of a high degree. When the temperature falls to a temperature lower than that of the narrow softening range during the spinning step, there takes place a rapid crystal growth and the molten polypivalolactone is already in an essentially undrawable condition which is never seen in other molten polymers. Accordingly, the taken-up fiber fails to acquire the effect of the drawing which is carried out in the next drawing step. In the present invention, therefore, it is necessary that the polymer is given such a spinning deformation ratio as will cause the polymer to possess, during spinning, a fiber structure which is oriented beyond the minimum value required ordinarily. The spinning deformation ratio which brings about such a fiber structure can be obtained by appropriately selecting the individual spinning conditions, and especially, the size of the orifice, the rate of extrusion, the take-up speed and the spinning atmosphere around the spinneret, and also by the application of a high draft. It is to be noted that this spinning atmosphere does not require any such strict control of the temperature or humidity of the atmosphere as is necessary in the spinning of nylon or polyethylene terephthalate. The spinning deformation ratio has to be determined by taking into consideration the fact that the molecular weight of polypivalolactone is very closely associated with the rheological property of polypivalolactone when the latter is melted and also with the spinning conditions employed. In view of the fact that, in the present invention, the workability in the spinning process is markedly improved as is represented by the improved spinnability of the molten polymer and the improved detachability of the molten polymer from the nozzle, it is possibleto obtain a desired fiber under such conditions that the spinning deformation ratio is set at a relatively small value. In order to determine a spinning deformation ratio which is suited for attaining the objects of the present invention, an experiment to spin fibers from polypivalolactones having various mean molecular weights, after these polymers were blended with the aforesaid additive, was conducted at a spinning temperature ranging between 240 degrees centigrade and 310 degrees centigrade. From the results of this experiment, it has been found that the preferred spinning deformation ratio A which is necessary in the second step must satisfy the relation which is expressed by the following Equation 1 with respect to the respective intrinsic viscosity (1;):

Generally, the higher the melt-spinning temperature is, the easier it becomes to increase the value of the spinning deformation ratio A. The effect of increasing the value of A can be obtained also by the employment of a reduced spinning pressure and also by the use of a larger size orifice of the spinneret and further by increasing the take-up speed. In the event, however, that the spinning temperature exceeds 310 degrees centigrade, the control of the melt viscosity at the time of spinning and the control of the spinning conditions become diflicult, owing to the reasons, including thermal decomposition, as have been previously described. Thus, there is a limit to the increase in the fluidity of the polymer and to the resulting improvement in the spinnability which may be eifected by elevating the spinning temperature. Furthermore, the use of a larger size orifice of the spinneret will result in a fluctuation in the extrusion rate of the polymer at the discharge edge of the orifice in the spinneret, and this makes it diflicult to obtain a fiber having a uniform fiber size. This also leaves a problem to be solved concerning the control for effecting stable operation. In the manufacture of an undrawn polypivalolactone fiber, it is to be noted that this polymer is of such a nature that its melt viscosity increases as the molecular weight of the polymer is increased, which results in reducing the feasibility of operation. Polypivalolactone, on the other hand, has the characteristic that a tenacious fiber can be obtained even if it is spun under conditions where the spinning deformation ratio is relatively small.

The employment of the additive in the present invention brings forth such effects that the fluidity of the polymer at the time of its being melted is increased, that the spinnability of the molten polymer is markedly enhanced and that the detachability of the molten polymer from the nozzle is improved. The employment of the additive is further useful from the aspect of uniformizing the size of the obtained fiber and, therefore, this is particularly advantageous in the spinning of a polypivalolactone having such a high molecular weight as has been described above.

A fiber which is given a required spinning deformation ratio in the second step is then transferred to the third step. What is the most unusual of the physical properties of polypivalolactone, is that this polymer crystallizes rapidly as time passes and that it attains an extremely high degree of crystallinity as is pointed out in the aforementioned paper of R. Thiebaut et al. and also in the French Patent No. 1,231,163. Such changes in the undrawn fiber due to the lapse of time not only hampers the orientation of the molecular chains at the time the fiber is drawn and constitutes the cause for a brittle fiber, but also causes numerous cracks to develop in the direction perpendicular to the direction in which the fiber is drawn, and may bring about the formation of an opaque fiber.

10 However, a fiber which is produced by melt spinning after said polymer has been admixed with the aforesaid additive, possesses an ability to reduce the adverse effect caused by the lapse of time, when compared with a fiber obtained from a polymer not containing an additive and spun under the same spinning conditions.

It has been further confirmed that, in view of the fact that these additives, even those having the highest density, have a melting point which is lower by at least 1'00 degrees centigrade than that of polypivalolactone, they provide an appropriate lubricating effect acting between the molecular chains of polypivalolactone, and that the degree of orientation of the undrawn fibers obtained from polypivalolactone containing such additives is always higher than the degree of orientation of the undrawn fibers obtained from polypivalolactone not containing additives and that the use of the additives is effective in the improvement of the orientation of fibers.

As has been stated, the difficulties which are otherwise encountered in the first and the second steps can be markedly improved by the employment of the additives. Also, this employment of additives serves to provide a very high enhancement of the effect of orientation of the spun fiber in the third or the drawing step and contributes to the improvement in the tensile strength and elongation of the obtained drawn fiber. Moreover, the desired object can be attained by conducting the drawing at a temperature lower than that required for the drawing of a fiber spun from the polymer not containing an additive. In case spinning is carried out at such a spinning deformation ratio as is desired in the present invention, or in other words, in case the spinning deformation ratio A satisfies the Equation 1, the drawing operation can be performed at such low temperatures as are defined by the following Equations 2 and 3:

T;-765.2R +420R (2) The melting point of said additive wherein: R represents the degree of orientation of an undrawn fiber.

What should be especially noted here is the boundary condition on the drawing temperature T C. in the above Equation 3. Specifically, in case the drawing is conducted at a temperature higher than the melting point of the additive employed, the effect of orientation of the molecular chains of polypivalolactone is essentially saturated and the fluidizing and plasticizing functions of the additive would only meaninglessly accelerate the sliding of the molecular chains of polypivalolactone to such an extent that it would become no longer useful in controlling the essential orientation of the polymer. Also, the glass-transition temperature of polypivalolactone has been found to be approximately 15 degrees centigrade based on dynamic mechanical measurements. In industrial practice also, it is economically as well as technologically disadvantageous to conduct the drawing at a temperature corresponding to or lower than room temperature. As a conclusion, by performing the drawing under the conditions defined by the Equations 2 and 3, a smooth and stable operation not affected by the changes due to lapse of time can be insured and a very effective orientation is effected by the drawing so that the fiber is stabilized at a desired appropriate degree of elongation, and thus a transparent, uniform and tenacious drawn fiber can be obtained without the least development of milky-like opaque stripes and cracks in the fiber.

The draw ratio is appropriately determined to be within the range of value between 1.5 and 10.0 so as to be in accord with the excellent elongation property of the individual undrawn fibers. In the preferred embodiment of the present invention, the value of the spinning deformation ratio A in the second step has to be taken into account in the determination of the proper draw rate. Since the degree of orientation of the undrawn fiber increases with an increase in the value of A, it is possible to carry out the third step at a reduced draw rate, and therefore, the final fiber property can be stabilized by a small drawing operation in the order of merely adjusting the residual degree of elongation of the undrawn fiber. In case A takes a relatively small value, the draw rate is required to take as large a value as possible within the aforementioned range in order to impart sufiicient tensile strength to the fiber. This drawing operation requires no special machinery or equipment, and such operation can be accomplished by the use of any known wet-type or dry-type drawing apparatus.

There is shown hereunder, in Table 1, one example of the values of the physical properties of the polypivalolactone fiber manufactured according to the aforesaid three steps, as compared against those of the fibers obtained according to the methods of the prior art.

As is clearly understood from Table 1, the fiber obtained according to the method of the present invention exhibits a markedly improved fiber property as compared with known fibers, and has an adequate degree of crystallinity, and shows a very small shrinkage in boiling water, and possesses a stabilized fiber property.

Among the various desirable properties of a synthetic fiber, the one which is very important from the viewpoint of developing the utility of the fiber is the heat-setting ability of such fiber. For example, the density value of 1.20 (corresponding to the degree of crystallinity of 78.8 percent) of the fiber described in U.S. Pat. No. 2,658,055, as is quoted in Table 3, is close to the maximum degree of crystallinity which this polymer can attain, and this leads to the assumption that the fiber has already lost its heat-setting ability. In contrast to this, the fiber manufactured according to the method of the present invention shows an appropriate density value of 1.17 or less (corresponding to the degree of crystallinity of 58 percent or less), leaving a difference of 20 percent or more in the degree of crystallinity from that of the fiber of the prior art. Therefore, this means that the fiber of the present invention has a sufficient heat-setting ability. According- 1y, there are achieved the following advantages that an excellent crimped yarn can be manufactured from the fibers of the present invention by utilizing this heatsetting ability of the fibers and by the use of a known mechanical crimping method, such as the twisting-settinguntwisting method, false twisting method and the stuff-inbox method, and also, that the extension percentage of crimp and the recovery percentage of crimp of the obtained crimped fiber can be markedly superior in conjunction with the intensive degree of orientation, the degree of crystallinity and the Youngs modulus of the fiber. Moreover, as has been described, the performance of the method of the present invention does not require any special machinery or equipment, but any known apparatuses, such as conventional melt-spinning apparatus and drawing apparatus can be utilized without requiring any modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The degree of orientation R which is used in the description of the following embodiments is of a value calculated by first determining the azimuthal X-ray diffraction pattern of the peak at 15.4 degrees, 20, and then 12 applying the half width B thereof to the following equation:

Example 1 To batches of polypivalolactone having an intrinsic viscosity n of 1.5 were added, separately, 0.2 percent, 2 percent, 6 percent and 10 percent by weight of parafiin (made by Wako Jun-yaku C0.) composed principally of. pentatriacontane and having melting points ranging from 70 degrees Centigrade to 73 degrees centigrade. The resulting mixtures were melted by heating. The molten mixtures were stirred so that the additives were thoroughly mixed with the polymer. The melt viscosity of the resulting mixtures was measured. This measurement was conducted by the use of Koka-type flow tester (made by Shimazu Seisakusho) and under the following conditions. Specifically, the molten mixtures were extruded at 250 degrees centigrade and under a pressure of 10 kg/cm. through nozzles 1 mm. in length and 0.3 mm. in orifice diameter. The extrusion rate Q (cc.) per unit time was measured. From the obtained extrusion rate the apparent melt viscosity 1 (poise) was calculated by the following equation:

where in:

r represents the radius (cm.) of the nozzle. P represents the pressure (dyne/cmF).

L represents the length (cm.) of the nozzle. Q represents the extrusion rate (cc./sec.).

The results of the measurements are shown in the following Table 1a:

As is obvious from Table 1a, samples containing paraffinic hydrocarbons were confirmed to have an increased fluidity when melted and to exhibit satisfactory spinnabil ity also at relatively low temperatures.

Example 2 Using a spinneret equipped with 10 orifices, each being 0.5 mm. in diameter, molten polypivalolactone having an intrinsic viscosity of 1.45 was extruded at a meltspinning temperature of 270 degrees centigrade into an atmosphere held at 22 degrees centigrade and at a relative humidity of percent.

Various undrawn fibers having various degrees of orientation (R), caused by varying the spinning deformation ratio A which was eifected by changing the take-up speed when the filaments were extruded under the aforesaid conditions, were wound on a take-up bobbin. Aside from the above, a mixture was prepared by using the same polypivalolactone and by adding thereto three percent by weight of solid paraflin (made by Wako Jun-yaku Co.)

composed chiefly of triacontane and having a melting point of 64 degrees centigrade. This mixture was spun under the same conditions as those described above, to obtain undrawn fibers. In view of the knowledge, as described in Example 1, that the addition of paraffin leads to an increase in the fluidity of polypivalolactone when melted and also to an improved spinnability and an improved detachability of the molten polymer from nozzle, the spinning of the paraflin-containing polypivalolactone was carried out at a temperature 10 degrees centigrade lower than the aforesaid spinning temperature. The de- 13 gree of orientation, tensile strength and fiber size fluctuation percentage of these undrawn fibers are shown in the following Table 2. The fiber size fluctuation percentage was measured in accordance with JIS-L1074 and calculated by the following equation:

Fiber size fluctuation pereentage= 100 Swipe-ow TABLE 4 Residual elon- Draw Draw Tensile Elon- Knot Loop Sample gation temperture ratio strength gation strength strength Number R ercen C (X) (g /d) (perce (g -I (e Appearance of fi 1 0,63 10 60 Operation not feasible because of frequent breakage of fiber. 353 4. 5 1. 5 32 1. 2 2. 2 Excellent, transparent. 295 3. 5 1.4 26 1. 2. 0 White opacity with cracks. 610 6. 5. 0 28 4. 3 9.1 Excellent, transparent.

4. 0 3. 5 29 3.1 6. 2 Good. 7.0 7.2 30 6. 5 12.4 Excellent 4.0 5.2 36 4.7 9.7 Good. 7. 0 8. 1 25 7. 2 13. 3 Excellent.

wherein:

n represents the total number of measurements taken.

As is shown in Table 4, undrawn fibers not containing parafiin had a greatly restricted draw ratio because :c represents the value in each measurement (fiber size). 25 of their reduced residual elongation, and became White represents the overall average value.

and opaque after being drawn. Microscopic observation As is clear from a comparison of the values for the respective undrawn fibers in Table 2, the fiber size fluctuation percentages of those undrawn fibers admixed with parafiin are very small. This is because the rheological property of the polymer at the time of spinning Was markedly improved by the addition of paraffin and because the spinnability and the detachability of the molten polymer from the nozzle were also extremely enhanced. Thus, a remarkable advantage is obtained both in the operation and in the property of the produced fibers. Furthermore, the samples added with paraffin are noted to be of a markedly increased degree of orientation and tensile strength over those not admixed with paraflin.

The result of the measurements of the changes in the elongation of the undrawn fibers of this example with lapse of time from immediately after being spun is shown in the following Table 3:

TABLE 3 Elongation percent In 1 In 2 In 3 hour hours hours Sample Number Right after R being spun In hours In 50 hours 1 0r less.

of such drawn fibers showed numerous cracks developed therein.

Fibers containing paraffin, however, exhibited a markedly improved draw ratio, with the result that a smooth drawing operation was accomplished with no appreciable development of cracks in the obtained fibers, and the drawn fibers were transparent. In particular, the increased draw ratio of the fibers due to the addition of parafiin was extremely effective for the improvement of the orientation and the tenacity of the fiber, and the effect of the use of this additive was markedly apparent in each of the characteristics of tensile strength, knot strength and loop strength.

Example 3 To samples of polypivalolactone having an instrinsic viscosity (7 of 1.5 were admixed, separately, five percent and 10 percent by weight of polyethylene (Sumikathen G-806, made by Sumitomo Chemical Co., Ltd.) having a melt index of 50, and also to a separate sample 10 percent by weight of partially oxidized polyethylene (AC629, made by Allied Chemical Co. of U.S.A.) with melting point of 97 degrees centigrade and molecular weight of 2,000. The resulting mixtures were melted by heating, respectively, followed by thorough mixing by stirring. The melt viscosity of the resulting mixtures was measured in the same manner as was described in Example 1 and the apparent melt viscosity (1 (poise) was calculated from the extrusion rate. The result of the measurement is shown in the following Table 5:

As is clear from Table 5, the samples containing polyethylene or partially oxidized polyethylene showed an increased fiuidity when melted and had a satisfactory spinnability even at relatively low temperatures.

Example 4 made by Eastman Co. of USA.) having a molecular weight of 1,500 and a melting point of 92 degrees centigrade to said polypivalolactone. The mixtures were subjected, respectively, to spinning and drawing in the same manner as that described above, and the obtained fibers were designated as the Fibers (III) and (IV) of the Using polypivalolactone having an intrinsic viscosity present invention, respectively. Their fiber properties are (1 of 1.21, this polymer was melt spun through an exshown in the following Table 7:

TABLE 7 Undrawn fiber Drawn fiber Residual Fiber size elon- Tensile Elon- Knot Loop fluctuation gation strength gatlon, strength strength percentage Sample R (percent) (gr./d.) percent (gr./d.) (gr./d.) (percent) Control fiber (II) 0. 78 310 2.0 21 1.5 3.0 17.? Fiber (III) of the present invention 0.83 630 6.2 45 6.0 10.5 6. 4 Fiber (IV) of the present invention 0.84 590 7.2 33 6.5 12.1 7.0

truder under the following conditions, namely, at a spinp 6 ning temperature of 260 degrees centigrade and by the A copolymer of ethylene and maleic acid was prepared use of a spinneret having 20 orifices each having a diamby the following process. Methyl alcohol and di-terteter of 0.3 mm. and at a spinning deformation ratio of butyl-peroxide were mixed together at the rate of 15 300. Thus, undrawn fibers were obtained. Control fibers parts and 10 parts by weight per hour, respectively. Into 1 were prepared by drawing these d fib o this mixture was dissolved maleic acid at the rate of 20 3.5 times the original length at 60 degrees Centigrade. P y Weight P hOIlI and the feshlhhg InlXhlTe W Aside from the above, a sample consisting of the aforecohtlmllously forced y p h elevahoh P p Into said polypivalolactone and admixed with 1.5 percent by a Into thls Feactlon tube m at 175 weight of Polyethylene (its mean molecular weight begrees g ggg was f ethylene which was ing 28,000) having a melt index of 25, and a sample adg eres gg a g g mixed with 1.1 percent by weight of partially oxidized 6 mac Ion pm He was fawn mm t m e at O1 eth lane (AC 629 made b Allied Chemical Co of the rate of 340 parts by welght per hour. The withdrawn {3 y 1 ht of 2 000 h a product was distilled to remove unreacted substances 3 mean m0 ecu at Yvelg therefrom. Thus, an ethylene copolymcr containing 2.4 melting P 97 dagrees a e w spun and 35 mol percent of maleic acid as the comonorner was obdrawn, respectively, under conditions similar to those detained at the rate of 289 parts by Weight per hour scribed above. The fibers thus obtained were designated percent by Weight f the Obtained ethylene t Fibers and P the Preseht ihvehhohi respec' polymer was added to polypivalolactone having an iny The h p p f 0f thfise three klhds 0f fibers trinsic viscosity (1;) of 1.03, and the mixture was melt spun are shown in the following Table 6: 40 using a heat grid-type melt-spinning apparatus and under TABLE 6 Undrawn fiber Drawn fiber Residual Tensile Elon- Knot Loop Young's Fiber size elongation strength gation strength strength modulus fluctuation Sample R (percent) (gr./d.) (percent) (gr./d.) (gr./d.) (kg/cm?) (percent) Control fiber (I) 0. 71 280 1.6 12 1.0 2.5 455 15.9 Fiber (1) of the present invention. 0.80 560 6.4 37. 5. 7 10.2 460 6.8 Fiber (II) of the present invention. 0.81 620 6.2 40 5.6 10.0 450 5.9

Example 5 the conditions, i.e., by the use of a spinneret having 20 I orifices each having a diameter of 0.35 mm. at a spin- Uslhg Polyplvalolactohe havlhg ah lhtllhslc vlscoslty ning temperature of 265 degrees Centigrade and at the l) of -h thfi P y Was S131111 under the follow" spinning deformation ratio of 450, to produce undrawn g cohdltlohs, at a Splhhlhg temperature of 275 fibers. Thereafter, the undrawn fiber was drawn to 4.1 flegffies chhtngrmie y thedlse of a splhhefet times the original length at 70 degrees centigrade, The E 20 f h each f a fhameter of and fiber thus obtained was designated as the Fiber (V) of at & p g ratio of Thus, uhdlafflh the present invention. Fibers obtained in exactly the same fibers were o taln d- T fibers h f i y dfaWlhg manner as that described above with the exception that said undrawn fibers to 4.0 times their original length at h h l copolymer was not dd d t th olymer IOOfh temperature were Used 35 Control fiber D- Next, were designated as the control fiber (III). The fiber propa mixture which Was pr par d by addi g 55 p c y erties of these two kinds of fibers are shown in the folweight of polyethylene (with a molecular weight of lowing Table 8:

TAB LE 8 Undrawn fiber Drawn fiber Residual Tensile Elon- Knot Loop Youngs Fiber size elongatlon strength gation strength strength modulus fiuctuation Sample R (percent) (gr./d.) (percent) (gr./d.) (gr./d.) (kg/cm?) percentage Control fiber (III) 0. 270 1.9 18 1.5 2.7 390 13.8 Fiber (V) of the present invention 0. 79 580 5. 7 40 5, 5 1o. 2 440 6, 0

24,000 and a melting point of 110 degrees centigrade) Example 7 to the aforesaid polypivalolactone prior to being spun, and another mixture prepared by adding 1.5 percent by The changes of elongability with lapse of time of the weight of partially oxidized polyethylene (Epolene LVE, respective undrawn fibers obtained in Examples 4 through 6, measured from the time immediately after being spun are shown in the following Table 9:

TABLE 9 Elongation (percent) Right after In 1 In 2 In 3 In 20 In 50 Sample being spun hour hours hours hours hours Control fiber (I) 280 10-20 Control fiber (I 310 245 230 205 Control fiber (III) 270 1 l Fiber (1) of the present invention 560 540 520 515 Fiber (II) of the present invention" 620 605 595 595 Fiber (III) of the present invention- 630 610 610 600 Fiber (IV) of the present invention- 590 575 575 575 Fiber (V) of the present invention 580 560 530 530 1 Or less.

As is clear from the above table, the control fibers showed a sharp reduction in elongability and became brittle due to the rapid crystallization caused by the lapse of time. In contrast to this, the fibers of the present invention invariably showed a minimized effect of the changes due to lapse of time and the crystallization velocity was retarded. It has been proved that the fibers of the present invention can retain drawability for an extended period of time.

Example 8 Polypivalolactones having an intrinsic viscosity (1;) of 1.10, 1.45 and 1.72, respectively, were extruded into an atmosphere held at 22 degrees centigrade and a relative humidity of 65 percent, using a spinneret having 10 orifices each having a diameter of 0.5 mm., and at a meltspinning temperature in the range between 260 degrees centigrade and 280 degrees centigrade. The value of the spinning deformation ratio A was varied by changing the take-up speed during winding the filaments extruded under the foregoing conditions, to thereby produce undrawn fibers having various degrees of orientation R. The relationship between this R and the tensile strength (meas ured based on JIS-L-1073) is shown in the following Table 10:

TABLE 10.RELATIONSHIP BETWEEN (1;), A, R AND TEN- SILE STRENGTH OF UNDRAWN POLYPIVALOLACTONE FIBERS Spinning tempera- Take-up Tensile ture speed strength Sample number (1;) C.) (rm/min.) R A (gr./d.)

As is clear from Table 10, the tenacity, for example, the tensile strength G (gr./d.), of these undrawn fibers (not containing parafiinic hydrocarbons) markedly increases with an increase in the degree of orientation R and almost independently of the value of (1;). It has been found that, between G and R, there is an established relationship which is expressed by the following Equation 4:

G-=ll.38R l3.06R+3.90 (4) Thus, it will be understood how greatly the tensile strength of the undrawn polypivalolactone fibers depends on the degree of orientation. In case polypivalolactone is used, this degree of orientation R is determined primarily by the value of the spinning deformation ratio A of the Formula 1 which is applied to the polymer during the spinning step.

Next, three percent by weight of commercial solid parafiin (made by Wako Jun-yaku Co.) composed principally of triacontane and having a melting point of 64 degrees centigrade was added to each of the samples shown in Table 10, and the mixtures were spun under the same fibers is shown in the following Table 11. Since the addition of parafiin has the effect of increasing the fluidity of polypivalolactone when melted and of improving the spinnability and the detachability of molten polymer from the nozzle, the operation was conducted by reducing the spinning temperature by 10 to 15 degrees centigrade. The indication of the sample is made in such manner that, for example, for the fiber obtained by admixing parafiin to Sample ll, the identifying term 1-1a is used. This is applied to other samples also. Thus, Where an additive is used the letter a is afiixed to the end of the corresponding serial number.

TABLE ll.-RELATIONSHIP BETWEEN (1;), A, R AND TE-N SILE STRENGTH OF UNDRAWN FIBERS ADMIXED WITH PARAFFIN IN AN AMOUNT 3% BY WEIGHT Spinning tempera- Take-up Tensile ture speed strtngth Sample number (1;) C.) (m./Inin.) R A (EL/d.)

at 0.8 40 0. L10 250 300 0.85 090 0.84 400 0.89 930 1.18 188 3'5 1. 18 8'3;

When the undrawn fibers shown in Table 10 are compared with those of Table 11, it is noted that the paraflin, which is added, serves to markedly improve the rheological property when the polymer is spun and to greatly enhance the spinnability and also the detachability of molten polymer from the nozzle, and furthermore, it minimizes the fiber size fluctuation of the obtained undrawn fibers. Thus, the marked advantages of the use of parafiin are observed in both the operation and the fiber property. The improved rheological property further permits the spinning to be easily carried out even at a low temperature, and, as is shown in the following Table 12, it brings forth an effect that a reduction in the viscosity of polymer can be arrested.

TABLE 12 Before After being being Sample No. Parafiin spun spun 1-1, 1-4 Not added" 1. 10 0.95 Added 1.10 1.01 Not added- 1. 45 1. 18 ded 1. 45 1. 35 Not added 1. 72 1. 24 ded 1. 72 1. 60

paraffin over those fibers not admixed with such additive, even when the former is given, during the spinning step, a spinning deformation ratio A identical to that of the latter which is not admixed with the additive.

Example 9 The result of the measurements of the tenacity of the fibers resulting from drawing is shown in the following Table 14:

TABLE 14.-TENACITY OF THE DRAWN FIBERS Tensile Knot Loop Sample Strength Elongation strength strength Number (gr./d.) (percent) (gr./d.) (gr./d.)

TABLE I3.-DRAW CONDITIONS AND THE FEASIBILITY OF OPERATION Degree of orientation R of Residual Draw Draw undrawn elongation temperaratio fiber (percent) ture (0.) (X) Feasibility of operation 0.70 211 3.0 White opaque with cracks. 0.70 211 3.0 d. 0. 82 620 6. Excellent 0.86 299 Room temperature. 3.6 Good. 0.89 640 o. 7.0 Excellent. 0.63 60 Operation impracticable due to frequent breakage of fiber.

0.63 10 120 1.5 Good. 0. 70 353 60 4.5 Excellent. 0.78 295 Room temperature. 3.5 White opaque with cracks. 0.85 610 6.5 Excellent. 0.87 3.5 Good. 0. 89 6. 5 Excellent.

Because of the poor drawability and the frequent break- As is shown in Table 14, the effect of the addition of age of fibers, It Was dlfi'lclllt t0 Perfectly Carry i paraffin is markedly displayed in each of tensile strength, drawing of the Sample 2-1. The Sample 2--a= containing knot Strength and loop strength.

a paraffinic additive; however, showed a superior drawability even when the drawing was conducted at the Exam 1810 same draw temperature as that for the Sample 2-1. p

In the drawing of Sample 2-1, the d'lfliculty in the operation can be eliminated by elevating the draw tem- 2 1 iy fi a havmg aninmnslc vdoclty perature to a considerable extent. However, the feasibility 2 o were um admufedi sePaIate1Y f the Operation of Sample was Still inferior to with paraflinlc hydrocarbons having various molecular Sample a. Likewise While Sample was not poor weights, were spun, respectively, through melt extruders. in its d bilit it turned White and Opaque ft being The molten mixtures were extruded into an atmosphere drawn. By optical microscopic examination, development held at 20 degrees Cemlgfade and a relative humidity of numerous cracks was observed. However, Sample 1-212: f 70 percent, using spinnerets each having 10 orifices admixed with parafiin showed a markedly increased draw ranging in diameter from 0.2 mm. to 1.5 mm., and at ratio even when it was drawn at the same draw temperaa melt-spinnin temperature f 260 degrees entigrade, 11m? 35 that 9 Sample and the drawing 531K216 The filaments extruded under these conditions were wound 1-211 Was easlly p Although the Whlte QP on a take-up bobbin at various take-up speeds ranging sgmple cizuld P t ig by the z z 8 from 200 m./min. to 500 m./min., and by giving various fiefiga wt (116215511; :rf, 2121s er property C 111113 0 e were drawn and the fiber properties of the drawn fibers The eifect of the paraffin can be readily understood g gi g gg i g g g g. g g i gl also from a comparison of Sample 2-2 with Sample bt d d h f 53 0 e 2-2a. In particular, the increase in the draw ratio due 55 o alne un Yawn ers 15 5 Own In a e to the introduction of paraffin is extremely effective for the improvement of the degree of orientation and also the tenacity of the fibers.

Also, the conditions under which said undr-awn fibers were drawn and the fiber properties of the drawn fibers are shown in Table 16.

TABLE 15.-UNDRAVVN FIBERS Description Melting point Molec- (melt Amount Tensile Sample ular index) added strength Number Kind (manufacturer) weight C. (percent) A (gr-.id.)

300 0. 82 a 0 i 140 0.49 b Paraflin composed principally oi nonadeeane 20 0 33 $13 8 c Solid paraffin composed principally of pentatriacontane.... 500 kg g8 133 d. PaTrItiilly oxidized polyethylene (Epolene, made by Eastman or). of 1, 500 02 8 e- .Pat ialiy oxidized polethylene (AC-629), made by Allied Chemical 2, 000 91 8 o. i Low density polyethylene (Sumikathen (3-806, made by Smni- 24, 000 11060); g-g

tomo Chemical Co.) 0 44 g High density polyethylene (Hizex 1100.7, made by Mitsui Chemical 34, 000 1' 9 (1 g 0 350 36 TABLE 16 Draw Tensile Elonga Sample Amount Draw ratio Density strength tion Number added temperature (X) (gr./cc.) gr./d.) (percent) Room temperature 2. 9 1. 165 5. 3 27 a 50 3.1 1.169 2. 1 32 0. 5 Room temperature 4. 9 1. 164 6. 5 29 1.0 do 4.9 1.168 7.4 26 1. 0 Room temperature 6. 5 1. 163 6. 7 36 c 3. 0 so 7. 0 1.166 8.2 31 d i l. 0 Room temperature- 6.0 1.162 7. 6 29 5.0 do. 6.0 1.150 8.7 1. 0 6. 2 1.168 8. 0 26 e 5. 0 Room temperatur 5.8 1.157 7.8 34 f 3. 4. 5 l. 155 7. 0 32 5. 0 l. 141 4. 4 28 4. 5 l, 158 6. 2 33 g 5. 0 1.142 1. 0 39 As is shown in Table 15, the lower the molecular we1ght EXAMPLE 12 of the additive, the higher becomes the fluidity of the polymer at the time of melting, Accordingly, a great effect of the use of such additive can be displayed even when it is used in a small amount, and specifically, the additive, though small in the amount used, will impart satisfactory spinnability and drawability to the polymer. As is also clear from Table 16, ultimately, equal fiber properties can be obtained independently of the kind or type of the additives used. Table 16 also shows the result of the study on the effect given by the draw temperature. In Sample f and Sample g, it is noted that in case the amount of polyethylene added is in excess of 10.0 percent by weight which is defined by the present invention, the drawing does not fully contribute to the improvement of orientation.

EXAMPLE 11 To polypivalolactone powder having an intrinsic viscosity (1 of 1.22 was added 2.8 percent by weight of partially oxidized polyethylene (AC-629, made by Allied Chemical Co.) having -a molecular weight of 2,000 and a melting point of 97 degrees centigrade, and thereafter the mixture was thoroughly mixed together by a V-type blender for one hour. The resulting mixture was extruded through a spinneret having six orifices each having a diameter of three mm., at the temperature of 260 degrees centigrade in the nozzle, and of 230 degrees centigrade at a site below the hopper, by using a screw-type melt extruder. The molten polymer extruded from the nozzles at the rate of 80 gr./min. was passed through quenching rollers of 30 cm. in diameter and thereafter was left to drop downward by its own weight and to solidify. Then, the solidified polymer was cut into lengths of four mm. by a cutter designed for the manufacture of chips to thereby manufacture polypivalolactone chips. These chips were used as the charge stock for the spinning. In carrying out the melt spinning of this sample, it was required to set the spinning deformation ratio at 160 or more from the definition made by the conditional Equation 1 described previously in this specification.

These chips were melt extruded into an atmosphere held at 25 degrees centigrade and a relative humidity of 70 percent under the conditions, i.e., by the use of a screw-type melt extruder, at the spinning temperature of 260 degrees centigrade in the nozzle, and of 210 degrees centigrade below the hopper, by the use of a spinneret having 20 orifices each having a diameter of 0.5 mm., at the extrusion rate of 9.3 gr./min., at the take-up speed of 400 m./min. and at the spinning deformation ratio of 180. As a result, undrawn fibers having R=0.87 and a size of 208 d./20 fil. were obtained. These undrawn fibers were drawn to 6.0 times the original length at 60 degrees centigrade, with the result that tenacious drawn fibers having a monofilament size of 1.5 d., a tensile strength of 6.4 gr./d., an elongation of 33 percent, a Youngs modulus of 460 kg./mm. a knot strength of 5.7 gr./d., a loop strength of 10.2 gr./d. and a shrinkage in boiling water of 2.8 percent (all these measurements are based on J IS-L-1073), were manufactured.

To powder polypivalolactone having an intrinsic vis cosity of 1.03 was added 4.5 percent by weight of a substance of powder form which was prepared by dissolving a low density polyethylene (Sumikathen G806, made by Sumitomo Chemical Co.) having a molecular weight of 24,000, a density of 0.917, a melting point of degrees centigrade and a melt index of 50, in heated xylene so as to be coercively emulsified and separated out in powder form. The mixture was then stirred for one hour by a V-type blender for thorough mixing. The resulting mixture was made into polypivalolactone chips in a manner similar to that employed in Example 11. From the conditional Equation 1, the spinning deformation ratio which is applied to this polymer having said intrinsic viscosity was required to be 280 or more. Using a heat grid-type melt-spinning apparatus, and under the conditions, i.e., by the use of a spinneret having 28 orifices each having a diameter of 0.4 mm., at a spinning temperature of 260 degrees centigrade, at an extrusion rate of 12 gr./min., at a take-up speed of 500 m./min. and at a spinning deformation ratio of 300, said chips were melt spun into an atmosphere held at 20 degrees centigrade and a relative humidity of 70 percent, with the result that undrawn fibers having R=0.85 and a size of d./ 28 fil. were obtained. Continuously thereafter, the undrawn fibers were drawn to six times the original length at 60 degrees centigrade, and as a result, tenacious drawn fibers having an excellent fiber property, i.e., having a monofilament size of 1.2 d., a tensile strength of 5.2 gr./d., an elongation of 38 percent, a Youngs modulus of 430 kg./m1n. a knot strength of 4.8 gr./d., a loop strength of 9.3 gr./d. and a shrinkage in boiling water of 2.7 percent, were manufactured.

Example 13 A copolymer of ethylene and methacrylic acid having a copolymeric mol ratio of 97:3 was prepared in the same manner as that in Example 6. To polypivalolactone having an intrinsic viscosity (1;) of 1.70 was added three percent by weight of the obtained copolymer, and the mixture was shaped into chips. Using a screw-extruder equipped with a spinneret having eight orifices each having a diameter of 0.4 mm., and under the conditions, i.e., a spinning temperature of 270 degrees centigrade, at a take-up speed of 500 m./min., at a spinning deformation ratio of 110, the chips were melt extruded into an atmosphere held at 18 degrees centigrade and a relative humidity of 65 percent, and the spun fibers were then drawn to 3.5 times the original length at room temperature, and thus, excellent drawn fibers having a size of 30 d./ 8 fil., a tensile strength of 5.2 gr./d., an elongation of 41 percent, a Youngs modulus of 435 kg./mm. a shrinkage in boiling water of 3.2 percent a knot strength of 4.9 gr./d., a loop strength of 9.3 gr./ d. and a fiber size fluctuation of 4.0 percent were obtained. The fibers obtained from polypivalolactone not admixed with an additive and spun and drawn under exactly the same conditions as those described above showed a tensile strength of 3.9 gr./d.,

23 an elongation of 34 percent, a Youngs modulus of 435 kg./cm. a shrinkage in boiling water of 3.1 percent, a knot strength of 3.6 gr./d., a loop strength of 7.0 gr./d., and a fiber size fluctuation of 14.3 percent.

Example 14 To polypivalolactone having an intrinsic viscosity (7;) of 2.0 was added 3.5 percent by weight of polyethylene oxide having an average molecular weight of 6,000. In a manner similar to that in Example 11, the mixture was shaped into chips which were melt extruded by the use of a screw extruder. Under the spinning conditions, i.e., by the use of a spinneret having 18 orifices each having a diameter of 0.25 mm, at a spinning temperature of 275 degrees centigrade, at an extrusion rate of 12.6 gr./min., at a take-up speed of 400 m./min. and at a spinning deformation ratio of 40, the molten mixture was extruded into an atmosphere held at 22 degrees centigrade and a relative humidity of 70 percent, with the result that undrawn fibers of R=0.86 and having a size of 240 d./ 18 fil. were obtained. These undrawn fibers were drawn 3.6 times the original length at 50 degrees centigrade, and as a result, drawn fibers having a size of 68 d./18 fil., a tensile strength of 5.4 gr./d., an elongation of 37 percent, a tensile recovery at five percent, elongation of 99 percent, a Youngs modulus of 412 kg./mm. and a density of 1.158 were obtained. These drawn fibers were then processed to give false twisting under the conditions of 3,500 T./m., a first feed rate of minus two percent, a second feed rate of plus eight percent and a temperature of 170 degrees centigrade. These processed fibers were of excellent properties, i.e., an extension percentage of crimp of 195 percent and a recovery percentage of crimp of 99 percent. Further, the same drawn fibers were subjected to the Banlon process according to the stuff-in-box method and under the conditions, i.e., a temperature of 175 degrees centigrade, a. take-up speed of 350 m./min., a stufiing pressure of 17 gr. and a roller pressure of four pounds. These processed fibers had an excellent property which was represented by an extension percentage of crimp of 105 percent.

Example To powder polypivalolactone having an intrinsic viscosity (1 of 2.40 was added 3.0 percent by weight of polyethylene glycol having a molecular weight of about 2,000. In a manner similar to that employed in Example 11 the mixture was thoroughly blended together and then made into chips. Using a screw-type melt extruder, and under the conditions, i.e., by the use of a spinneret having 12 orifices each having a diameter of 0.2 mm., at a spinning temperature of 277 degrees centigrade, at an extrusion rate of 9.0 gr./min., at a take-up speed of 670 m./min. and at a spinning deformation ratio of 30, the chips were melt spun into an atmosphere held at degrees centigrade and a relative humidity of 65 percent, to obtain undrawn fibers having R=0.90 and a size of 120 d./ 12 fil. The resulting undrawn fibers were cold drawn at a room temperature to 7.5 times the original length, and tenacious drawn fibers having a monofilament size of 1.33 d., a tensile strength of 8.2 gr./d., an elongation of percent, a Youngs modulus of 650 kg./mm. a knot strength of 7.5 gr./d. and a loop strength of 13.4 gr./d., were obtained.

Example 16 To powder polypivalolactone having an intrinsic viscosity (1;) of 2.00 was added a solution of benzene having a molecular weight of about 500 and a melting point of 70 degrees centigrade in such manner that the pure parafi'in content in said polymer was 5.5 percent by weight. While heating and stirring the mixture, ben- Zene was evaporated therefrom. After the remaining substance was thoroughly dried up, it was melt spun using the spinning apparatus employed in Example 8. Under the spinning conditions, i.e., by the use of a spinneret having one orifice of 0.2 mm. in diameter, at a spinning temperature of 275 degrees centigrade, at an extrusion rate of 0.4 gr./min., at a take-up speed of 500 rn./min. and at a spinning deformation ratio of 40, the polymer was melt spun in an atmosphere held at 23 degrees centigrade and a relative humidity of 75 percent. As a result, an undrawn fiber having R=0.88 and a size of 7.5 d./1 fil. was obtained. Continuously therefrom, the undrawn fiber was drawn at room temperature to five times the original length. Thus, a tenacious drawn fiber having a monofilament size of 1.5 d., a tensile strength of 7.0 gr./d., an elongation of 30 percent, a Youngs modulus of 525 kg./mm. a knot strength of 6.6 gr./d. and a loop strength of 11.8 gr./d., was obtained.

Example 17 To polypivalolactone having an intrinsic viscosity (v7) of 3.35 was added three percent by weight of tricresyl phosphate, and in a manner similar to that employed in Example 11, the mixture was made into chips. Using a screw extruder and under the conditions, i.e., by the use of a spinneret having one orifice of 0.5 in diameter, at a spinning temperature of 280 degrees centigrade, at an extrusion rate of 5.7 gr./min., at a take-up speed into an atmosphere held at 20 degrees centigrade and a relative humidity of 65 percent, with the result that an undrawn fiber having R=0.89 and a size of 72 d. and having a residual elongation of 492 percent was obtained. This undrawn fiber was then drawn at a room temperature to 5.1 times the original length, and thus, a tenacious and excellently uniform filament having a fiber size of 14.9 d., a fiber size fluctuation of 6.2 percent, a tensile strength of 8.4 gr./d., an elongation of 26 percent, a Youngs modulus of 680 kg./mm. a knot strength of 8.1 gr./d. and a loop strength of 15.9 gr./d., was obtained.

Example 18 To polypivalolactone having an intrinsic viscosity '1; of 1.6 was added 2.5 percent by weight of trioctadecyl phosphite, and in the manner described in Example 11, chips were produced. From the Equation 1, the spinning deformation ratio required for the melt spinning of said chips was 63 or more. Using a heat grid-type melt-spinning apparatus, and under the conditions, i.e., by the use of a spin-neret having 18 orifices each having a diameter of 0.4 mm, at a spinning temperature of 275 degrees centigrade, at a take-up speed of 500 m./min. and at an extrusion rate of 12.3 gr./min., the chips were melt spun into an atmosphere held at 20 degrees centigrade and a relative humidity of percent. As a result, undrawn fibers having R=0.88, and a size of 249 d./ 18 fil., were obtained. Continuously thereafter, the undrawn fibers 'were drawn at room temperature to 3.7 times the original length, and thus, tenacious filaments having a size of 70 d./ 18 fil., a tensile strength of 6.1 gr./d., an elongation of 35 percent, a Youngs modulus of 520 kg/mm. and a shrinkage in boiling water of 3.0 percent were obtained.

Example 19 The respective drawn fibers obtained in Examples 11 through 13 were made into crimped fibers. Specifically, a part of them was subjected to a crimping process by the use of a false twisting machine of 08-3 type made by Earnest Scrugg Co. (England), under the conditions of processing which were: the speed of the feed-in roller being 63.5 m./min., the surface temperature of the heater being 210 degrees centigrade, the revolution of the spindle being 200,000 rpm. and the speed of the delivery roller being 61 m./min. The sample thus obtained was designated as Sample A. Another part of the drawn fibers was subjected to crimping process by the use of a stutf-in-box type crimping machine of B-type made by Bancroft Co. of U.S.A., at the heat-setting temperature of 200 degrees centigrade. The obtained sample was designated as Sample 25 B. The result of the measurement of the extension percentage of crimp and the recovery percentage of crimp of these two types of fibers (measured based on JIS-L- 1077) is shown in the following Table 17:

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A drawn, tenacious polypivalolactone fiber having a maximum density of 1.17 and a heat-setting ability, which is formed of a composition comprising a polymer consisting essentially of polypivalolactone and a small amount of a least one organic compound selected from the group consisting of polyethylene, partially oxidized polyethylene, copolymers of ethylene and u,,B-6thylBI1iC unsaturated carboxylic acids, polyethylene oxide having a molecular weight of at least 600, and an alkane, C H wherein r2514, said organic compound being uniformly distributed in said polymer.

2. A fiber according to claim 1, wherein said organic compound is a polyethylene having a melt index of at least 20.

3. A fiber according to claim 1, wherein said organic compound is a polyethylene having a melt index of at least 30.

4. A fiber according to claim 1, wherein said organic compound is selected from the group consisting of at least one copolymer of ethylene and at least one a,fi-ethylenic unsaturated carboxylic acid selected from the group con sisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, citraconic acid and mesaconic acid.

5. A fiber according to claim 1, wherein said organic compound is a polyethylene oxide having a molecular weight of at least 600.

6. A fiber according to claim 1, 'wherein said organic compound is an alkane,

n 2n+2 wherein: ngl4.

7. A fiber according to claim 1, wherein the amount of said organic compound contained in the polymer is from 0.1 to 10.0 percent by weight of the total weight of the composition.

8. A fiber according to claim 1, wherein the amount of said organic compound contained in the polymer is from 1.0 to 6.0 percent by weight of the total weight of the composition.

References Cited UNITED STATES PATENTS 2,996,466 8/1961 Kessler et al 26028 2,676,945 4/1954 Higgins 26045.7

MURRAY TILLMAN, Primary Examiner C. J. SECCURO, Assistant Examiner US. Cl. X.R. 

